Stump cutter drive system

ABSTRACT

A stump cutter includes a cutter wheel rotatable about a cutter wheel axis, the cutter wheel supported by a boom for sweep movements about a vertical cutter wheel sweep axis, and the cutter wheel is supported by the boom for tilt movements about a horizontal cutter wheel tilt axis. A prime mover is configured to drive the cutter wheel about the cutter wheel axis. A mechanical driveline provides power transmission from the prime mover to the cutter wheel, the mechanical driveline including a final drive cutter wheel gearbox positioned along the cutter wheel axis, and a swivel gearbox assembly including two right angle gearboxes joined with a swivel joint therebetween. The swivel joint between the two right angle gearboxes forms a driveline swivel axis. A downstream one of the two right angle gearboxes includes an output shaft connected to an input shaft of the final drive cutter wheel gearbox.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 63/010,199, filed Apr. 15, 2020, and U.S. ProvisionalPatent Application No. 63/035,215, filed Jun. 5, 2020, the entirecontents of both of which are incorporated by reference herein.

BACKGROUND

The present invention relates to machines for material reduction of treestumps by cutting and/or grinding, and more particularly to a drivesystem for such machines.

Conventional stump cutters are well known. These machines commonlyinclude a rotating cutter wheel driven by a prime mover (e.g., a gas ordiesel engine). The cutter wheel, while rotating, is advanced toward thestump and moved laterally across the face of the stump to reduce thestump material by cutting and/or grinding. Often, the cutter wheel isautomatically advanced across the face of the stump in a sweepingmotion. The cutter wheel is mounted to one end of a boom which is, inturn, pivotally mounted on a support frame. Hydraulic boom swingcylinders are used to pivot the boom about the pivot point to move thecutter wheel back and forth across the face of the stump to reduce it.Advancing the cutter wheel toward the stump is accomplished by separatehydraulic tilt cylinders that causes the boom to tilt within a verticalplane.

In some stump cutters, the engine is operably connected to the cutterwheel by belts that facilitate rotation of the cutter wheel. In otherstump cutters, the engine powers a hydraulic pump that in turn drives ahydraulic motor coupled to the cutter wheel. Despite the nature of thepower transmission connection, between the prime mover and the cutterwheel, careful design consideration is required to accommodate theunique operational movement requirements of the boom. In some cases, theprime mover can be directly located on the boom to alleviatecomplications associated with power transmission through an articulatingstructure, however, this may reduce stability and may limit theacceptable range of motion, for example, operating an internalcombustion engine at a significant angle from horizontal is undesirableand may limit engine options.

SUMMARY

In one aspect, the invention provides a stump cutter including aboom-mounted cutter wheel rotatable about a cutter wheel axis. Thecutter wheel is supported by a boom for sweep movements about a verticalcutter wheel sweep axis so that the cutter wheel sweeps along an arcuatepath within a horizontal plane. The cutter wheel is supported by theboom for tilt movements about a horizontal cutter wheel tilt axis sothat the cutter wheel tilts along an arcuate path within a verticalplane. A prime mover is configured to drive the cutter wheel about thecutter wheel axis. A mechanical driveline is configured to provide powertransmission from the prime mover to the cutter wheel. The mechanicaldriveline includes a final drive cutter wheel gearbox positioned alongthe cutter wheel axis, and a swivel gearbox assembly including two rightangle gearboxes joined with a swivel joint therebetween. The swiveljoint between the two right angle gearboxes forms a driveline swivelaxis. A downstream one of the two right angle gearboxes includes anoutput shaft connected to an input shaft of the final drive cutter wheelgearbox.

In another aspect, the invention provides a stump cutter including amainframe and an engine supported on the mainframe such that acrankshaft of the engine extends horizontally when the stump cutter issituated in an operative position on a horizontal ground surface. Acutter wheel support structure extends from the mainframe to support acutter wheel at a distance from the mainframe, the cutter wheel supportstructure having: a sweep subframe pivotally connected to the mainframedefining a vertical cutter wheel sweep axis, and a tilt subframepivotally connected to the sweep subframe defining a horizontal cutterwheel tilt axis on one end and with a cutter wheel right angle gearboxmounted to the opposite end with an output shaft for supporting thecutter wheel and an input shaft. A jointed driveline include a firstright angle gearbox fixedly secured with respect to the engine andhaving a horizontal input shaft connected to the engine crankshaft,wherein a vertical output shaft of the first right angle gearbox definesa driveline sweep axis parallel to the cutter wheel sweep axis. Thejointed driveline includes a second right angle gearbox pivotallymounted on the first right angle gearbox about the driveline sweep axis,wherein the second right angle gearbox includes a horizontal outputshaft, defining a driveline tilt axis parallel to the cutter wheel tiltaxis. The jointed driveline includes a third right angle gearboxpivotally mounted on the second right angle gearbox about the drivelinetilt axis, wherein the third right angle gearbox includes an outputshaft extending in a direction toward the cutter wheel right anglegearbox. A driveshaft is configured to provide power transmission fromthe output shaft of the third right angle gearbox to the input shaft ofthe cutter wheel right angle gearbox. A gearbox alignment structureextends along the driveshaft and has a first portion fixed to the cutterwheel right angle gearbox and a second portion fixed to the third rightangle gearbox and configured to limit misalignment between the inputshaft of the cutter wheel right angle gearbox and the output shaft ofthe third right angle gearbox so that the orientation of the secondright angle gearbox relative to the first right angle gearbox about thedriveline sweep axis, and the orientation of the third right anglegearbox relative to the second right angle gearbox about the drivelinetilt axis are controlled by the combination of the driveshaft and thegearbox alignment structure when the cutter wheel support structuremoves relative to the mainframe about the cutter wheel sweep and tiltaxes.

In yet another aspect, the invention provides a stump cutter including aprime mover supported above a ground surface by a mainframe of the stumpcutter. A cutter wheel is configured to be driven about a cutter wheelaxis by the prime mover. The cutter wheel is supported for sweepmovements about a vertical cutter wheel sweep axis so that the cutterwheel sweeps along an arcuate path within a horizontal plane, and thecutter wheel is supported for tilt movements about a horizontal cutterwheel tilt axis so that the cutter wheel tilts along an arcuate pathwithin a vertical plane. A mechanical driveline between the prime moverand the cutter wheel includes a first right angle gearbox including avertical output shaft defining a driveline sweep axis parallel to thecutter wheel sweep axis; a second right angle gearbox pivotally mountedon the first right angle gearbox about the driveline sweep axis, thesecond right angle gearbox including a horizontal output shaft defininga driveline tilt axis; a third right angle gearbox mounted on the secondright angle gearbox and including an output shaft; and a cutter wheelright angle gearbox having an output shaft extending along the cutterwheel axis, the cutter wheel right angle gearbox having an input shaftconnected to the output shaft of the third right angle gearbox.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a first perspective view of a stump cutter according to afirst embodiment of the present disclosure.

FIG. 1B is a second perspective view of the stump cutter of FIG. 1A.

FIG. 2 is a side elevation view of the stump cutter of the firstembodiment. The nearside track is removed to reveal a boom swingcylinder.

FIG. 3 is a bottom plan view of the stump cutter of the firstembodiment.

FIG. 4 is a perspective view of the stump cutter of the firstembodiment. Numerous housings, covers, and shielding pieces are removedto reveal the underlying mechanicals.

FIG. 5 is a perspective view similar to FIG. 4 , although taken from theopposite side of the boom and showing the boom in a position that istilted further downward.

FIG. 6A is a side elevation view of the stump cutter with the boom inthe position of FIG. 5 .

FIG. 6B is a side elevation view of the stump cutter similar to FIG. 6A,but with the boom in a raised position.

FIG. 7A is a plan view of the stump cutter with the boom in the downwardposition of FIGS. 5 and 6A.

FIG. 7B is a plan view of the stump cutter with the boom raised to aneutral position.

FIG. 8A is a front view of the stump cutter of the first embodiment,showing the boom swung to a left side.

FIG. 8B is a perspective view of the stump cutter having the boom in theposition of FIG. 8A.

FIG. 8C is a plan view of the stump cutter having the boom in theposition of FIGS. 8A and 8B.

FIG. 9A is a front view of the stump cutter of the first embodiment,showing the boom swung to a right side.

FIG. 9B is a perspective view of the stump cutter having the boom in theposition of FIG. 9A.

FIG. 9C is a plan view of the stump cutter having the boom in theposition of FIGS. 9A and 9B.

FIG. 10A is a front view of a gear-drive transmission of the stumpcutter of the first embodiment.

FIG. 10B is a right side elevation view of the gear-drive transmissionof FIG. 10A.

FIG. 10C is a perspective view of the gear-drive transmission of FIGS.10A and 10B.

FIG. 11 is a front elevation view of a stump cutter according to asecond embodiment of the present disclosure.

FIGS. 12A to 12C are right side elevation views showing the stump cutterof FIG. 11 in raised, neutral, and lowered boom positions, respectively.

FIG. 13 is a plan view of the stump cutter of the second embodiment.

FIG. 14 is a perspective view of a stump cutter according to a thirdembodiment of the present disclosure.

FIG. 15 is a side elevation view of the stump cutter of FIG. 14 ,including a partial cutaway to illustrate the sweep cylinder.

FIG. 16 is a plan view of the stump cutter of FIGS. 14 to 15 .

FIG. 17 is a front elevation view of a stump cutter of FIGS. 14 to 16

FIG. 18 is perspective view of a stump cutter according to a fourthembodiment of the present disclosure.

FIG. 19 is a side elevation view of the stump cutter of FIG. 18 .

FIG. 20 is a plan view of the stump cutter of FIGS. 18 and 19 .

FIG. 21 is a perspective view of a stump cutter according to a fifthembodiment of the present disclosure.

FIG. 22 is a side elevation view of the stump cutter of FIG. 21 .

FIG. 23 is a side elevation view of a stump cutter according to a sixthembodiment of the present disclosure.

FIG. 24 is a side elevation view of a stump cutter according to aseventh embodiment of the present disclosure.

FIG. 25 is a side elevation view of a stump cutter according to aneighth embodiment of the present disclosure.

FIG. 26 is a plan view of the stump cutter of FIG. 25 .

FIG. 27 is a side elevation view of a stump cutter according to a ninthembodiment of the present disclosure.

FIG. 28 is a plan view of the stump cutter of FIG. 27 .

FIGS. 29A to 29C are partial side elevation views of a stump cutteraccording to a tenth embodiment of the present disclosure, showing theboom in three different tilt positions.

FIGS. 30A to 30C are plan views of the stump cutter of FIGS. 29A to 29C,showing the boom in three different sweep positions.

FIG. 31 is a perspective view of a stump cutter according to an eleventhembodiment of the present disclosure, including a gimbal and CV joint.Numerous housings, covers, and shielding pieces are removed to revealthe underlying mechanicals.

FIG. 32A is a side elevation view of the stump cutter of FIG. 31 withthe boom tilted upward.

FIG. 32B is a side elevation view of the stump cutter of FIG. 31 withthe boom tilted downward.

FIG. 33A is a plan view of the stump cutter of FIG. 31 with the boomswung to a first side.

FIG. 33B is a plan view of the stump cutter of FIG. 31 with the boomswung to a second side.

FIG. 34 is a perspective view of the stump cutter of FIG. 31 with theboom swung to the first side.

FIG. 35 is a perspective view of the stump cutter of FIG. 31 with theboom swung to the second side.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

FIGS. 1A and 1B illustrate a stump cutter 100 for materially reducingtree stumps by cutting and/or grinding with a rotatable cutter wheel102. The stump cutter 100 includes a frame, or “mainframe,” 104 thatsupports a prime mover 106 (FIG. 4 ) for driving the cutter wheel 102and a movable boom 108, a distal end of which rotatably supports thecutter wheel 102. As described in detail below, the boom 108 is mountedrelative to the mainframe 104 to enable motion in the horizontal planein a first direction, herein referred to as sweep movement, moving thecutter wheel across a stump and also motion in the vertical plane,raising/lowering up/down with respect to the ground, herein referred toas tilt movement, moving the cutter wheel down as a stump is cut fromthe top or moving up to raise the cutter wheel for repositioning. Thesweep movement as illustrated provides movement of the cutter wheel 102along an arcuate path within a horizontal plane. The illustratedembodiment provides arcuate movement with a fixed radius, about a sweeppivot axis A. The tilt movement provides movement of the cutter wheel102 along an arcuate path within a vertical plane. The illustratedembodiment provides arcuate movement with a fixed radius, about a tiltpivot axis F. The stump cutter 100 is movable under its own power alongthe ground by a ground drive system having wheels and/or tracks 110. Theground drive system enables motion of the cutter wheel in the horizontalplane in a second direction. To control operation of the stump cutter100, including movement along the ground, drive of the cutter wheel 102,and movements of the boom 108, the stump cutter 100 can include operatorcontrols 112. The operator controls 112 can be provided on a fixedcontrol panel on the stump cutter 100 or may be provided on a removableand/or remote control. A cover or hood 114 covers an upper portion ofthe cutter wheel 102 and may be pivotable by a linkage during verticaltilting of the boom 108 so as to maintain a relatively constantorientation through the movement range of the boom 108. Additionalshielding 116 may be provided to extend from the boom 108 behind and atleast partially around the cutter wheel 102 to limit the throwing ofchips during reduction of the stump. The stump cutter 100 is provided asan integrated or single-purpose work machine, as opposed to a detachablework implement for a tractor or other device. In other words, the boom108 with the cutter wheel 102 and the prime mover 106 are on-boardcomponents with respect to the mainframe 104. However, aspects of thedisclosure may also be provided in “mounted” stump cutters configuredfor attachment to a general purpose tractor, for example where themainframe is mounted to a three-point linkage of a tractor.

For horizontal direction sweeping, the boom 108 includes a sweepsubframe 118 pivotally coupled to the mainframe 104 about a verticalsweep axis A (FIGS. 1B and 3 ), or “cutter wheel sweep axis” about whichthe cutter wheel 102 is configured to sweep. The sweep subframe 118 hasa C-shape profile providing separate upper and lower pivot joints 120with the mainframe 104. Sweep motion of the boom 108 is carried out inresponse to actuation (extension or retraction) of a sweep cylinder 122(FIGS. 2 and 3 ) mounted between the mainframe 104 and the sweepsubframe 118. For vertical cutter wheel movement, which may be referredto as tilt or lift, a pivot joint 124 is provided between a boom tiltsubframe 126 and the sweep subframe 118. The tilt subframe 126 supportsthe cutter wheel 102 at an end opposite the pivot joint 124. As such,the cutter wheel 102 tilts about a horizontal axis F (FIGS. 1B and 4 ),or “cutter wheel tilt axis” through the pivot joint 124. Tilt motion ofthe tilt subframe 126 is carried out in response to actuation (extensionor retraction) of a tilt cylinder 128 mounted between the sweep subframe118 and the tilt subframe 126. The sweep and tilt cylinders 122, 128 canbe operated by hydraulic oil through at least one control valve assemblyand at least one hydraulic pump (not shown) supported on the mainframe104. As shown in FIGS. 6A and 6B, the tilt range can be 30 degrees ormore upward from horizontal, and 40 degrees or more downward fromhorizontal. As shown in FIGS. 8C and 9C, the sweep range can be 35degrees or more to either side from center. As discussed in furtherdetail below, the tilt subframe 126 forms a pivot joint 130 with adriveline alignment frame 132 extending from a portion of amulti-gearbox transmission 134. In the illustrated construction, thepivot joint 130 is provided by a ball joint.

From FIG. 4 onward, an engine cover 136 is removed, among other parts,to better illustrate a driveline, in particular a jointed driveline,that drives rotation of the cutter wheel 102 from the prime mover 106.The driveline is entirely mechanical in construction, rather than ahydraulic fluid drive, and consists of gearboxes, shafts, and joints inthe illustrated embodiment. Modified forms of mechanical drivelines,some of which additionally include a belt drive for example, areprovided in several additional embodiments following the description ofthe first embodiment. The prime mover 106, which is in someconstructions an internal combustion engine having a crankshaft, issupported on the mainframe 104 behind the boom 108. Thus, the primemover 106 does not move with the boom 108 during either of sweep ortilt. Although fixed to the mainframe 104, the prime mover 106 can besupported thereon by isolation mounts 138 (e.g., including resilientvibration absorbing material) such that there is an allowance for alimited range of relative movement. An output shaft 140 (FIG. 6A, e.g.,the internal combustion engine crankshaft) of the prime mover 106 isoriented horizontally along an axis B. A clutch 142 couples thehorizontal output shaft of the prime mover 106 with an input of themulti-gearbox transmission 134, in particular an input shaft 144 of afirst right angle gearbox 146 (FIGS. 10B and 10C). The first right anglegearbox 146, and more particularly a housing thereof, is fixedly securedto the prime mover 106. As illustrated, the first right angle gearbox ismounted to the engine through the clutch 142, or more particularly ahousing thereof. In the illustrated construction, the securement of thefirst right angle gearbox 146 is made by way of a plurality of removablefasteners through a mounting plate or flange 148, which may be separatefrom the gearbox 146 and the clutch 142 or integrated with at least oneor the other. Thus, the first right angle gearbox 146 is fixed with theprime mover 106 and not movable with the tilt or sweep of the boom 108.By being supported from the prime mover 106, the first right anglegearbox 146 will have limited restrained movement relative to themainframe 104 and sweep subframe 118, isolator-induced movementsresulting from the prime mover 106 being mounted on isolation mounts138, but is otherwise fixed or limited to a single operational positionwith respect to the mainframe 104. As such, and for brevity, the firstright angle gearbox 146 is sometimes referred to herein as the fixedgearbox 146. However, the multi-gearbox transmission 134 furtherincludes two additional right angle gearboxes 150, 152 forming a swivelgearbox assembly that is pivotally coupled to an output side of thefixed gearbox 146 in addition to accepting torque transmissiontherefrom. A driveline swivel shaft 170 (FIG. 10A) extends between thefixed gearbox 146 and the adjacent right angle gearbox 150 so as to formthe output shaft of the gearbox 146 and the input shaft of the gearbox150. The multi-gearbox transmission 134, and in fact the driveline as awhole to the cutter wheel 102, can be a fixed-ratio or single-speedpower transmission.

The swivel gearbox assembly formed by the two additional right anglegearboxes 150, 152 can pivot relative to the fixed gearbox 146 about afirst driveline swivel axis A, or “driveline sweep axis” along which thedriveline swivel shaft 170 extends. In the illustrated construction,this is the same axis A about which the sweep subframe 118 pivots on themainframe 104. In other words, the sweep axis for the boom 108 and thecommon axis shared between the fixed gearbox 146 and the swivel gearboxassembly 150, 152 are coincident and form the shared axis A. Althoughthis is a mechanically advantageous arrangement, it is contemplated toalternately have an offset between these two axes. The swivel gearboxassembly 150, 152 is swivel-mounted onto the gearbox 146, neithergearbox 150, 152 having a direct connection to the mainframe 104 or thesweep subframe 118. However, the downstream right angle gearbox 152 hasa partially-restrained connection with the tilt subframe 126 through thedriveline alignment frame 132 as described further below. The gearbox150 is coupled to the fixed gearbox 146 at a first gearbox-gearbox jointwith an interstitial bearing 154, e.g., a slewing bearing configured forlow speed back-and-forth oscillation. On the other hand, the two rightangle gearboxes 150, 152 are pivotally coupled to each other at a secondgearbox-gearbox joint with only internal bearings (e.g., two bearings ineach gearbox housing, not shown) supporting a driveline tilt shaft 156(integral shaft or connected shaft portions forming a common shaft)extending therebetween. The shaft 156 provides the output shaft ofgearbox 150 and the input shaft of the gearbox 152. FIG. 10A illustratesthe shaft 156 and how the housings of the gearboxes 150, 152 are thusspaced apart. However, it should be noted that the pivot or swivelconnections between adjacent gearboxes of the multi-gearbox transmission134 need not be made exactly in the manner illustrated. For example, thefirst and second gearbox-gearbox joints can each take the constructionof the other, resulting in the joint types being reversed among the twojoint locations or both joints having the same type of jointconstruction. According to the description of the illustrated embodimentand variations thereof, it will be appreciated that the gearboxes 150,152 are pivotally mounted on the directly upstream gearboxes 146, 150,respectively, whether or not there is a separate bearing, and whether ornot a coupling between the gearbox housings is provided.

As will be apparent from inspection of the drawings, boom sweepmovements are accommodated in the drivetrain by pivoting of thegearboxes 150, 152 together relative to the fixed gearbox 146 about thefirst driveline swivel axis A, while boom tilt movements areaccommodated in the drivetrain by pivoting the gearbox 152 relative tothe gearbox 150 about a second driveline swivel axis C. The axes A, Bremain orthogonal throughout operation by way of the construction of thefixed gearbox 146. The axes A, C remain orthogonal throughout operationby way of the construction of the intermediate gearbox 150. The axis Cis movable within a plane offset from the axis B (e.g., movable within ahorizontal plane below a horizontal plane containing the axis B). Thefinal gearbox 152 of the multi-gearbox transmission 134 is provided withan output shaft 158 rotatable about an axis D1 as shown in FIGS. 10A to10C. The axes C, D1 remain orthogonal throughout operation by way of theconstruction of the final gearbox 152. The multi-gearbox transmission134 provides for the output axis D1 to assume a wide range oforientations with respect to the axes A, B. The output axis D1 generallyfollows a direction of elongation between proximal and distal ends ofthe boom tilt frame 126. The output shaft 158 is connected with anupstream end of a driveshaft assembly 160 that extends alongside theboom tilt subframe 126 to a final drive right angle gearbox or “cutterwheel gearbox 162” that has an input axis D2 and input shaft 164arranged orthogonal from the cutter wheel axis E and output shaft 166(FIG. 7A). The cutter wheel gearbox 162 is fixedly secured to the boomtilt subframe 126 at an end thereof opposite the pivot joint 124 on thesweep subframe 118. The driveshaft assembly 160 includes telescopingdriveshaft portions and a U-joint 163 associated with each of thesetelescoping portions (FIGS. 6A, 8A, among others). This arrangementaccommodates the different kinematic motion during tilting of the tiltsubframe 126, about pivot 124, as compared to the tilt of the gearbox152, which pivots about the axis C that is spaced rearward (nearer theprime mover 106).

Although the driveshaft assembly 160 is jointed so as to afford someflexibility in length and misalignment of the axes D1, D2 not present ina one-piece or otherwise “fixed” driveshaft, the axial misalignment inparticular should be limited and further, angles in the two U-joints 163should be equalized to the extent possible. Control of the structure ofthe driveshaft assembly 160 in this way enables sinusoidal speedvariation in one U-joint 163 to be offset or canceled by that of theother U-joint 163 to obtain the overall effect of maintaining constantvelocity imparted to the cutter wheel 102 through each rotation. As canbe appreciated by those of skill in the art, the driveshaft assembly 160provides constant velocity power transmission without necessitating theinclusion of a constant velocity (CV) joint, per se, i.e., a singlejoint that, by its intrinsic structure, ensures constant velocity whenthe input/output are articulated. In order to provide mechanicalstructure to the flexible driveshaft assembly 160, the stump cutter 100includes a gearbox alignment structure or driveline alignment structureconsisting in part of a portion of the tilt subframe 126 (which is fixedto the cutter wheel gearbox 162) and the driveline alignment frame 132(which forms a torque arm fixed to the third right angle gearbox 152).As best shown in FIGS. 5, 8B and 8C, the gearbox alignment structureextends along the driveshaft assembly 160 and includes a plurality ofjoints, including the aforementioned pivot joint 130. The pivot joint130 is formed between the tilt subframe 126 and an intermediate arm 172.The intermediate arm 172 forms another joint, in particular a slidingjoint 174, with the driveline alignment frame 132 on the third rightangle gearbox 152. In other constructions, the configuration of the twojoints 130, 174 along the intermediate arm 172 can be reversed. Thesliding joint 174 provides a single translational degree of freedombetween the intermediate arm 172 and the driveline alignment frame 132(and with it, the third gearbox 152). The pivot joint 130 provides alimited range of motion about a joint axis extending perpendicular tothe axis formed by the translational degree of freedom, which in theillustrated construction is parallel to and offset from the axis D1 ofthe output shaft 158 of the third gearbox 152. The gearbox alignmentstructure maintains the axis D1 in a defined vertical plane 176 (FIG. 8Cwith the axis D2 of the input shaft of the cutter wheel gearbox 162) asthe gearbox 152 pivots about its axis C. The vertical plane 176 is fixedwith respect to the tilt subframe 126, and thus the plane 176 sweepswith the boom relative to the mainframe 104. Accordingly, the potentialmisalignment between the axes D1, D2 is limited. The driveline alignmentframe 132 also controls the rotational position of the two gearboxes150, 152 about the axis A during sweep.

The jointed driveline provided by the above structures, including themulti-gearbox transmission 134, the driveshaft assembly 160, and thecutter wheel gearbox 162 provides a compact and highly efficient mannerof power transmission while equipping the boom 108 with wide ranges ofsweep and tilt. Aside from the clutch 142, which resides immediatelydownstream of the prime mover 106, the entire driveline is comprised ofpositive, non-slipping transmission elements that establish permanent orcontinuous mechanical engagement. In other words, aside fromdisassembly, the power transmission path remains intact at all times andis not configured for selective disengagement. In some constructions,there is no clutch between the prime mover 106 and the driveline. Withor without a clutch, inefficiencies of power conversion (e.g.,mechanical to fluid pressure and back to mechanical) are largely orwholly avoided. Along the boom 108 with its numerous structural anddriveline pivots, minimal or no electric harnesses and/or hydraulichoses need pass through a pivot between the prime mover 106 and thecutter wheel 102. The illustrated driveline also allows the prime mover106 to remain in a fixed orientation on the mainframe 104 so that aconventional and economical internal combustion engine may reliably beutilized, as the engine's operating orientation is independent of theboom's articulation. The construction as illustrated also helps minimizeboom length for the stump cutter 100. Boom length is determined by thesweep angle, the total angle the boom 108 can sweep through in order toachieve a predetermined sweep distance. With a smaller allowable sweepangle, the boom needs to be longer to achieve the predetermined sweepdistance. In the illustrated construction, the allowable sweep angle hasno angular limitation resulting from the driveline. Reduced boom lengthhas the advantage of better stability, boom control, and footprint.

FIGS. 11 to 13 illustrate a stump cutter 200 of a second embodiment inwhich the final drive cutter wheel gearbox 162 is not fixedly secured atthe distal end of the tilt subframe 126, but rather is pivotally mountedto allow rotation of the cutter wheel gearbox 162. Except for thisdistinction, which is further described below along with relatedsupporting modifications, the stump cutter 200 conforms to the abovedescription of the stump cutter 100 and includes the features thereof,with like reference numbers as applicable. In order to provide thecapability for the cutter wheel gearbox 162 to swivel or pivot on thetilt subframe 126, an extra bearing 278 is provided. The bearing 278,for example a slewing bearing, can be provided between the cutter wheelgearbox 162 and the tilt subframe 126, either as an interstitialcomponent or integrated with the structure on one side or the other. Thebearing 278 is separate from high speed bearings needed to supportrotation of the cutter wheel 102 (and the output shaft of the cutterwheel gearbox 162). For example, the cutter wheel gearbox 162 caninclude one or more bearings internal to its housing, and at least onebearing 280 is provided to support a hub 282 of the cutter wheel 102 onthe tilt subframe 126. Because the cutter wheel gearbox 162 of FIGS. 11to 13 is not strictly fixed to the orientation of the tilt subframe 126,the pivot joint 130 of the prior embodiment is disposed of, and thegearbox alignment structure consists of only the sliding joint 174between the driveline alignment frame 132 fixed on the housing of thethird gearbox 152 and a similar second alignment frame 232 (e.g., torquearm fixed to the housing of the cutter wheel gearbox 162) extending fromthe cutter wheel gearbox 162 toward the first driveline alignment frame132. Thus, the gearbox alignment structure telescopes only, and does notarticulate. Although the U-joints 163 are illustrated as part of thedriveshaft assembly 160, and may be included for manufacturing andassembly convenience, the driveshaft assembly 160 only telescopes anddoes not articulate during movement of the boom 108. The axes D1, D2(out of the third gearbox 152 and into the cutter wheel gearbox 162)remain in alignment throughout operation of the boom 108, from the pointof manufacture. It is also noted that FIG. 13 illustrates anotherinterstitial bearing 154 provided between the second and third gearboxes150, 152 of the pivotally mounted swivel gearbox assembly, a featurethat was noted as optional in the preceding description, as it is in thestump cutter 200. In other words, the additional structural connectionprovided by the bearing 154 can be eliminated, provided that the shaftand internal gearbox bearings provide adequate strength.

FIGS. 14 to 17 illustrate a stump cutter 300 of a third embodiment inwhich the gearboxes 146, 150, 152, 162 are stressed frame elements forthe boom 108, and the individual subframes 118, 126 and pivots 120, 124are eliminated. Except for this distinction, which is further describedbelow along with related supporting modifications, the stump cutter 300conforms to the above description of the stump cutter 100 and includesthe features thereof, with like reference numbers as applicable.Elimination of the sweep and tilt subframes 118, 126 eliminates a loadpath for conveying boom loads to the mainframe 104. Rather, the boom 108of the stump cutter 300 transmits boom loads to the mainframe 104through the stressed elements of the driveline. In other words, theentire boom 108 is cantilevered from the prime mover 106 and the fixedright angle gearbox 146. The only joint supporting boom sweeping aboutthe axis A is the driveline swivel shaft 170 (and coaxial bearing(s),e.g., the interstitial bearing 154) between the fixed gearbox 146 andthe adjacent right angle gearbox 150 of the pivot-mounted swivel gearboxassembly (FIG. 10A). Likewise, the only joint supporting boom tilting(which pivots about the axis C rather than the offset tilt axis F) isthe driveline tilt shaft 156 (and coaxial bearing(s), e.g., internal tothe gearboxes 150, 152) between the pair of horizontally-adjacent rightangle gearboxes 150, 152 of the pivot-mounted swivel gearbox assembly(FIG. 10A). The sweep cylinder 122 is connected between the mainframe104 and a first driveline alignment frame 332A that is fixedly securedto the gearbox 150 that serves as the middle gearbox of thethree-gearbox transmission. The first driveline alignment frame 332A canbe mounted to the housing of the gearbox 150 with spacers 386 (e.g.,arranged along each of a plurality of threaded fasteners) to provideadequate clearance for the first driveline alignment frame 332A to clearthe fixed gearbox 146 during sweep. As shown in FIG. 15 , the tiltcylinder 128 is mounted to the first driveline alignment frame 332Aadjacent an upper end thereof. The second or distal end of the tiltcylinder 128 is mounted to the second driveline alignment frame 332Bthat extends between and fixedly secures the gearboxes 152, 162 togetherso that the axes D1, D2 are effectively a single axis, although thedriveshaft assembly 160 can still include the U-joints 163 for ease ofinitial assembly. The driveshaft assembly 160 need not be provided as atelescoping structure, as it will not change length during boommovements. The driveshaft assembly 160 can be partially or fullyenclosed by the second driveline alignment frame 332B, which ispartially cut away in FIG. 15 for illustration of the driveshaftassembly 160. The two driveline alignment frames 332A, 332B are onlyindirectly connected to each other through the pivotally-connectedgearboxes 150, 152 of the multi-gearbox transmission 134.

FIGS. 18 to 20 illustrate a stump cutter 400 of a fourth embodiment inwhich the gearbox 152 is eliminated, with boom tilt instead beingaccommodated by a CV joint 488. Except for this distinction, which isfurther described below along with related supporting modifications, thestump cutter 400 conforms to the above description of the stump cutter100 and includes the features thereof, with like reference numbers asapplicable. Rather than the gearbox 150 having the output shaft extendlaterally into the gearbox 152, the output shaft 156 from the gearbox150 extends directly to the driveshaft assembly 160 (refer back to FIG.10A for the output shaft 156, disregarding the gearbox 152). Thus, theaxis D1 is defined by the output of the gearbox 150, and the verticalplane 176 containing the driveshaft axes D1, D2 also contains the axisA, which is the sweep axis of both the driveline and the cutter wheel102. All three gearboxes 146, 150, 162 are arranged along the verticalplane 176. Virtually all of the misalignment between the axes D1, D2 isaccommodated within the CV joint 488 (i.e., all of the operational orpost-manufacture misalignment). However, a U-joint may still be includedfor ease of initial assembly. Although not apparent from the drawings,the gearbox 150 between the gearboxes 146, 162 can be fixedly secured tothe sweep subframe 118. The tilt subframe 126, a portion of which isremoved in FIG. 19 to show the driveline in its entirety, partiallysurrounds the driveshaft assembly 160 including the CV joint 488 (e.g.,portions of the tilt subframe 126 flank both lateral sides of thedriveshaft assembly 160).

FIGS. 21 and 22 illustrate a stump cutter 500 of a fifth embodiment inwhich, like the stump cutter 400, the CV joint 488 is provided so thatone of the gearboxes of the first embodiment can be eliminated. In thecase of the stump cutter 500, the second gearbox 150 is eliminated, withboom sweep instead being accommodated by the CV joint 488. As such, thegearbox 152 that extends to the driveshaft assembly 160 isswivel-mounted to the fixed gearbox 146. The fixed gearbox 146 isoriented so that the output shaft thereof extends horizontally ratherthan vertically. The output shaft of the fixed gearbox 146, which mayalso form the input shaft of the gearbox 152, does not form thedriveline sweep axis, but rather the driveline tilt axis C. Because theorientation of the output shaft of the gearbox 152 is free to swivel andwill follow the tilting orientation of the input shaft of the finaldrive cutter wheel gearbox 162, the cutter wheel gearbox 162 can befixedly secured to the end of the tilt subframe 126, but may alternatelybe swivel-mounted as in the second embodiment due to the presence of theCV joint 488. The boom 108 must be designed with proper clearance forsweep movement between the sweep subframe 118 and the gearbox 152, whichdoes not move during sweep. Although removed from the drawings forclarity in illustrating the driveline, the stump cutter 500 alsoincludes a driveline alignment frame between the gearbox 152 and thecutter wheel gearbox 162. The driveline alignment frame is of atelescoping structure by way of a sliding joint.

FIG. 23 illustrates a stump cutter 600 of a sixth embodiment in whichthe tilt subframe is replaced by a four-bar linkage lift system 626.Except for this distinction, which is further described below along withrelated supporting modifications, the stump cutter 600 conforms to theabove description of the stump cutter 100 and includes the featuresthereof, with like reference numbers as applicable. More particularly,the stump cutter 600 can be considered a modified version of the stumpcutter 200 of the second embodiment. The stump cutter 600 includes apivoting final drive cutter wheel gearbox 162, and the drivelinealignment structure includes only the sliding joint 174, which islargely obscured in the side elevation view of FIG. 23 . In someconstructions, the four-bar linkage lift system 626 can conform to thatof commonly-owned U.S. Pat. No. 8,783,308 (or aspects thereof), theentire contents of which are incorporated by reference herein. Due tothe four-bar arrangement, there is not a finite tilt axis at a fixedpoint on the sweep subframe 118. Rather than the cutter wheel 102following a circular path in side elevation view, the cutter wheel 102tilt motion follows a path defined by the links and pivots of thefour-bar linkage when actuated by the tilt cylinder 128. The tilt pathcan have a variable radius that is significantly larger (flatter path)in one portion of its travel. The use of the four-bar linkage liftsystem 626 is not limited to the details of this embodiment, and may beemployed with various other embodiments of the present disclosure,including those with a non-pivotally-mounted final drive cutter wheelgearbox 162 or those where one of the gearboxes 150, 152 is eliminated.

FIG. 24 illustrates a stump cutter 700 of a seventh embodiment in whichthe fixed gearbox 146 has a belt connection or belt drive 790 from theprime mover 106 rather than a shaft connection as in the earlierembodiments. Except for this distinction, which is further describedbelow along with related supporting modifications, the stump cutter 700conforms to the above description of the stump cutter 100 and includesthe features thereof, with like reference numbers as applicable. Moreparticularly, the stump cutter 700 is a modified version of the stumpcutter 400 of the fourth embodiment in which the gearbox 152 iseliminated, with boom tilt instead being accommodated by the CV joint488. However, the belt drive 790 can be applied to other embodiments ofthe present disclosure as well. The belt drive 790 is implemented byreorienting (with respect to the first embodiment) the input shaft 144of the fixed gearbox 146 by 90 degrees in a horizontal plane to extendlaterally rather than rearward toward the prime mover 106. The primemover output shaft 140 is also oriented laterally, parallel with theinput shaft 144 so that each shaft can have fixed therewith a pulley inline with the pulley of the other, and a belt can be wrapped around bothpulleys to establish power transmission drive from the prime mover 106to the fixed gearbox 146. The belt and pulleys can be smooth V-belts,ribbed belts, toothed belts, etc. Further a chain and sprockets may beused in lieu of the belt and pulleys, as belts and chains are bothexamples of flexible endless drive members. In some constructions, thebelt drive 790 can serve as an overload device and/or a speed reductiondevice.

FIGS. 25 and 26 illustrate a stump cutter 800 of an eighth embodiment inwhich the prime mover 106 is oriented with a vertical output shaft 140directly above the sweeping gearbox 150, the fixed gearbox 146 beingeliminated from the driveline. Except for this distinction, which isfurther described below along with related supporting modifications, thestump cutter 800 conforms to the above description of the stump cutter100 and includes the features thereof, with like reference numbers asapplicable. The bearing 154, e.g., a slewing bearing configured for lowspeed back-and-forth oscillation, supports the gearboxes 150, 152 of theswivel gearbox assembly directly from the prime mover 106. According tothis arrangement, the output of the prime mover 106 is arranged alongthe driveline sweep axis A (which is also the cutter wheel sweep axis asshown). In some constructions of the stump cutter 800, the prime mover106 having the vertical output shaft 140 is an electric motor that ispowered by a supply of electric current (e.g., from an on-board batterypack, fuel cell, etc.).

FIGS. 27 and 28 illustrate a stump cutter 900 of a ninth embodiment thatis a modified version of the stump cutter 800 of FIGS. 25 and 26 . Inthe stump cutter 900, the prime mover 106 having the vertical outputshaft 140 is not directly above the sweeping gearbox 150 on the axis A.Rather, the output shaft 140 extends along the axis B parallel to andoffset from the sweep axis A. An additional driveline element, e.g., abelt drive like the belt drive 790 of the stump cutter 700, connects theoutput shaft 140 of the prime mover 106 to the input of the gearbox 150(which is not shown). The belt drive 990 can be a speed reduction unit.The belt drive 990 can include a belt and pulleys (shown), or may bereplaced by a chain and sprockets, or a gear train in otherconstructions.

FIGS. 29A to 30C illustrate a stump cutter 1000 of a tenth embodiment inwhich the tilt subframe 1026 is directly pivoted on the mainframe 104,and the sweep subframe 1018 is pivotally supported by the mainframe 104through the tilt subframe 1026. Thus, the structures supporting sweepand tilt are effectively reversed. Additionally, the fixed gearbox 146is eliminated and the remaining gearboxes 150, 152 of the swivel gearboxassembly are vertically stacked along the driveline sweep axis A, whichin this embodiment again forms the cutter wheel sweep axis as well.Except for the distinctions described herein, the stump cutter 1000conforms to the above description of the stump cutter 100 and includesthe features thereof, with like reference numbers as applicable. Asshown in FIGS. 29A to 29C, tilting of the cutter wheel 102 isaccomplished by tilting the entire boom 108, including the tilt andsweep subframes 1026, 1018 about the cutter wheel tilt axis F at pivot124. As such, in the reverse of the stump cutter 100, the tilt axis F isfixed with respect to the mainframe 104, and the sweep axis A pivotswith respect to the mainframe 104 in response to tilt movements. A beltdrive 1090 like the belt drives 790, 990 can extend from the prime moveroutput shaft 140 to the input shaft of the gearbox 150, arranged alongthe cutter wheel tilt axis F. Both gearboxes 150, 152 tilt togetherrelative to the mainframe 104. Although the gearbox 150 first receivingthe drive power from the prime mover 106 is located below the secondgearbox 152, this can be reversed in other constructions. The tiltsubframe 1026 can be directly connected to the mainframe 104 or one ormore fixed extensions 1094 thereon as shown. The pivot joints 120support the sweep subframe 1018 as it extends outward to support thecutter wheel right angle gearbox 162 at a distal end thereof. Thedriveshaft assembly 160 may not experience changes length or angleduring sweep and tilt movements of the boom. Nevertheless, thedriveshaft assembly 160 can include telescoping portions and/or U-jointsas illustrated. The mechanical driveline including the driveshaftassembly 160 extends through the sweep subframe 1018 as best shown inFIGS. 30A to 30C. For example, the sweep subframe 1018 can include atleast two sides defining a cavity in which the driveshaft assembly 160is positioned. Thus, the driveshaft assembly 160 is at least partiallyshielded by the boom 108 as it is located at least partially within aperiphery of the boom 108, e.g., the sweep subframe 1018 thereof. FIGS.30A to 30C illustrate the sweep range in plan view with the boom 108 ina level un-tilted orientation.

FIGS. 31-35 illustrate a stump cutter 1100 of an eleventh embodiment.Although many basic elements of the stump cutter 1100 are similar tothose of the preceding description, the stump cutter 1100 represents asignificant fundamental departure from these in the way in which thedrive power and articulation are imparted to the boom 108. Inparticular, the boom 108 is supported on the mainframe 104 by a two-axisgimbal set, and the driveshaft assembly 1160 includes a CV joint 1188within the two-axis gimbal set, the CV joint 1188 accommodating both theboom tilt movements and the boom sweep movements. The two-axis gimbalset includes a gimbal subframe 1118 pivotally supported about the sweepaxis A with respect to the mainframe 104. Although the mainframe 104 isshown to include a hollow box portion for supporting the gimbal subframe1118 at upper and lower pivot joints 120 in the illustrated embodiment,other practical shapes (e.g., ring or C-shape) are optional for themainframe 104 to support the gimbal subframe 1118 for movement about thesweep axis A. The tilt subframe 1126 is pivotally supported at thelaterally-spaced pivot joints 124 about the tilt axis F with respect tothe gimbal subframe 1118. The gimbal subframe 1118 is formed as a hollowrectangular box, although this is merely one example of a hollow oropen-center shape that exists among others (e.g., ring or C-shape). Theinboard end of the tilt subframe 1126 includes a pair oflaterally-spaced attachment portions 1126A for connection at the pivotjoints 124 with the gimbal subframe 1118. The attachment portions 1126Aare nested within the gimbal subframe 1118 just as the gimbal subframe1118 is in turn nested within the hollow portion of the mainframe 104 toallow two-axis boom movements with the driveshaft assembly 1160 passingthrough the gimbal subframe 1118.

The sweep axis A and the tilt axis F intersect each other and define aplane, rather than being spaced away from each other as in the stumpcutter 100. In this limited respect, the stump cutter 1100 is similar tothe stump cutter 1000 of FIGS. 29A to 30C. However, rather than rightangle gearboxes accommodating the sweep and/or tilt at the inboard endof the boom 108, the stump cutter 1100 utilizes the gimbal subframe 1118and the CV joint 1188. The sweep and tilt axes A, F intersect each otherat the CV joint 1188 so that the CV joint can effectively accommodatethe full range of sweep and tilt for the boom 108. Because the boomsweep and tilt are inherently limited to an effective and practicalangular limit and have no need for a full 360 degrees of rotationcapability, the gimbal subframe 1118 need not provide exact intersectionof the axes A, F in all constructions, and instead a small offset may beprovided (e.g., 100 mm or less). In cases where the sweep and tilt axesA, F do not precisely intersect to define exactly one plane, each of thesweep and tilt axes A, F may still intersect the CV joint 1188. The CVjoint 1188 can be provided as a centered double cardan joint that cansmoothly accommodate sweep movements, tilt movements, and combinationsthereof, while maintaining constant velocity in the driveline to thecutter wheel gearbox 162. Although not required in all constructions,the illustrated construction provides the tilt subframe 1126 with a wide“L” shape in the side view and an angled gearbox 1177 at theintersection of the legs of the “L.” This arrangement provides aconvenient angle of attack for the cutter wheel 102, keeping the tiltsubframe 1126 largely behind an approach direction when cutting a stump.

The prime mover 106 can drive the driveshaft assembly 1160, includingthe CV joint 1118 from a fixed gearbox 1146. A clutch 142 can bepositioned between the prime mover 106 and the gearbox 1146 and thegearbox 1146 can provide a speed reduction. The gearbox 1146 can haveparallel or concentric input and output axes. For aiding assembly, thedriveshaft assembly 1160 can be variable-length or telescoping. However,the driveline length does not change as the cutter wheel 102 movesthroughout its range of travel. Between the angled gearbox 1177 and thefinal drive cutter wheel gearbox 162, a second driveshaft 1161 isprovided, and the second driveshaft 1161 may also be fixed-length. Eachof the driveshaft assembly 1160 and the second driveshaft 1161 caninclude a U-joint for the sake of convenience, although articulation iseffectively prohibited during operation. The mechanical drivelineincluding the driveshaft assembly 1160 and/or the second driveshaft 1161extends through the tilt subframe 1126 as best shown in FIG. 31(portions of the tilt subframe 1126 being removed for illustrationpurposes in the later figures). For example, the tilt subframe 1126 caninclude at least two sides defining a cavity in which at least onesection of the mechanical driveline is positioned. Thus, the mechanicaldriveline is at least partially shielded by the boom 108 as it islocated at least partially within a periphery of the boom 108, e.g., thetilt subframe 1126 thereof. It is noted that the illustrated exampleshows the mainframe 104 supporting the gimbal subframe 1118 about thesweep axis A, although the construction may be effectively reversed orturned on its side in another construction so that the mainframe 104supports the gimbal subframe 1118 about the tilt axis F and the cutterwheel 102 is in turn supported by an elongated sweep subframe. It isfurther noted that, to the extent that it is found desirable for anyreason, the sweep axis A may deviate from true vertical, just as thetilt axis F may deviate from true horizontal.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of one or more independent aspects of the inventionas described.

What is claimed is:
 1. A stump cutter comprising: a boom-mounted cutterwheel rotatable about a cutter wheel axis, wherein the cutter wheel issupported by a boom for sweep movements about a vertical cutter wheelsweep axis so that the cutter wheel sweeps along an arcuate path withina horizontal plane, and wherein the cutter wheel is supported by theboom for tilt movements about a horizontal cutter wheel tilt axis sothat the cutter wheel tilts along an arcuate path within a verticalplane; a prime mover configured to drive the cutter wheel about thecutter wheel axis; and a mechanical driveline configured to providepower transmission from the prime mover to the cutter wheel, themechanical driveline including a final drive cutter wheel gearboxpositioned along the cutter wheel axis, and a swivel gearbox assemblyincluding two right angle gearboxes joined with a swivel jointtherebetween, wherein the swivel joint between the two right anglegearboxes forms a driveline swivel axis, wherein a downstream one of thetwo right angle gearboxes includes an output shaft connected to an inputshaft of the final drive cutter wheel gearbox.
 2. The stump cutter ofclaim 1, wherein the prime mover includes an output shaft extendingalong a horizontal axis, the stump cutter further comprising a rightangle gearbox configured to pivotally support the swivel gearboxassembly about the driveline swivel axis and to convey power from theprime mover output shaft to an input shaft of an upstream one of the tworight angle gearboxes of the swivel gearbox assembly.
 3. The stumpcutter of claim 1, wherein the driveline swivel axis is coaxial with thecutter wheel sweep axis.
 4. The stump cutter of claim 1, wherein theprime mover includes an output shaft extending vertically along thedriveline swivel axis.
 5. The stump cutter of claim 1, wherein the primemover includes an output shaft extending vertically parallel to andoffset from the driveline swivel axis.
 6. The stump cutter of claim 1,wherein the driveline swivel axis accommodates one of the movements ofthe group consisting of: the cutter wheel tilt movements and the cutterwheel sweep movements, while an upstream one of the two right anglegearboxes is pivotally supported on the stump cutter to define anotherdriveline swivel axis accommodating the other one of the movements ofthe group consisting of: the cutter wheel tilt movements and the cutterwheel sweep movements.
 7. The stump cutter of claim 6, wherein theupstream one of the two right angle gearboxes is pivotally supported ona right angle gearbox that is fixed with respect to the prime mover. 8.The stump cutter of claim 6, wherein at least one of the drivelineswivel axes is/are not aligned with either of the cutter wheel sweepaxis or the cutter wheel tilt axis, and wherein the mechanical drivelinebetween the swivel gearbox assembly and the final drive cutter wheelgearbox includes at least one joint.
 9. The stump cutter of claim 1,wherein the prime mover is an internal combustion engine including anoutput shaft extending horizontally to an additional right angle gearboxon which the swivel gearbox assembly is pivotally mounted.
 10. The stumpcutter of claim 1, wherein the driveline swivel axis accommodates one ofthe movements of the group consisting of: the cutter wheel tiltmovements and the cutter wheel sweep movements, the mechanical drivelineof the stump cutter further comprising a constant velocity jointaccommodating the other of the movements of the group consisting of: thecutter wheel tilt movements and the cutter wheel sweep movements. 11.The stump cutter of claim 1, wherein the final drive cutter wheelgearbox is swivel-mounted on the boom, wherein a driveline alignmentstructure extending along the mechanical driveline between the swivelgearbox assembly and the final drive cutter wheel gearbox includes asliding joint.
 12. The stump cutter of claim 1, wherein the final drivecutter wheel gearbox is fixed-mounted on the boom, wherein a drivelinealignment structure extending along the mechanical driveline between theswivel gearbox assembly and the final drive cutter wheel gearboxincludes a sliding joint and a pivot joint.
 13. The stump cutter ofclaim 1, wherein the boom supporting the cutter wheel includes a sweepsubframe pivotally coupled to a mainframe of the stump cutter about thesweep axis, and the boom further includes a tilt subframe pivotallycoupled to the sweep subframe about the tilt axis.
 14. The stump cutterof claim 1, wherein the mechanical driveline includes one or both of: aspeed-reduction unit and a clutch between the prime mover and an inputshaft of an upstream one of the two right angle gearboxes.
 15. The stumpcutter of claim 1, wherein the final drive cutter wheel gearbox and theswivel gearbox assembly are stressed frame elements of the boom on whichthe cutter wheel is supported.
 16. A stump cutter comprising: amainframe; an engine supported on the mainframe such that a crankshaftof the engine extends horizontally when the stump cutter is situated inan operative position on a horizontal ground surface; a cutter wheelsupport structure extending from the mainframe to support a cutter wheelat a distance from the mainframe, the cutter wheel support structurehaving: a sweep subframe pivotally connected to the mainframe defining avertical cutter wheel sweep axis, and a tilt subframe pivotallyconnected to the sweep subframe defining a horizontal cutter wheel tiltaxis on one end and with a cutter wheel right angle gearbox mounted tothe opposite end with an output shaft for supporting the cutter wheeland an input shaft; a jointed driveline having: a first right anglegearbox fixedly secured with respect to the engine and having ahorizontal input shaft connected to the engine crankshaft, wherein avertical output shaft of the first right angle gearbox defines adriveline sweep axis parallel to the cutter wheel sweep axis, a secondright angle gearbox pivotally mounted on the first right angle gearboxabout the driveline sweep axis, wherein the second right angle gearboxincludes a horizontal output shaft, defining a driveline tilt axisparallel to the cutter wheel tilt axis, and a third right angle gearboxpivotally mounted on the second right angle gearbox about the drivelinetilt axis, wherein the third right angle gearbox includes an outputshaft extending in a direction toward the cutter wheel right anglegearbox; and a driveshaft configured to provide power transmission fromthe output shaft of the third right angle gearbox to the input shaft ofthe cutter wheel right angle gearbox; a gearbox alignment structureextending along the driveshaft and having a first portion fixed to thecutter wheel right angle gearbox and a second portion fixed to the thirdright angle gearbox and configured to limit misalignment between theinput shaft of the cutter wheel right angle gearbox and the output shaftof the third right angle gearbox so that the orientation of the secondright angle gearbox relative to the first right angle gearbox about thedriveline sweep axis, and the orientation of the third right anglegearbox relative to the second right angle gearbox about the drivelinetilt axis are controlled by the combination of the driveshaft and thegearbox alignment structure when the cutter wheel support structuremoves relative to the mainframe about the cutter wheel sweep and tiltaxes.
 17. The stump cutter of claim 16, wherein the driveline tilt axisand the cutter wheel tilt axis are offset.
 18. The stump cutter of claim16, further comprising a clutch between the engine and the first rightangle gearbox, the engine crankshaft being selectively connected to theinput shaft of the first right angle gearbox through the clutch.
 19. Thestump cutter of claim 16, wherein the cutter wheel right angle gearboxis fixed-mounted on the tilt subframe, wherein the gearbox alignmentstructure includes a sliding joint and a pivot joint.
 20. The stumpcutter of claim 16, wherein the second right angle gearbox is pivotallymounted on the first right angle gearbox by a driveline swivel shaftformed as one integral piece comprising both the output shaft of thefirst right angle gearbox and the input shaft of the second right anglegearbox, and further by at least one bearing, and wherein the thirdright angle gearbox is pivotally mounted on the second right anglegearbox by a driveline tilt shaft formed as one integral piececomprising both the output shaft of the second right angle gearbox andthe input shaft of the third right angle gearbox, and further by atleast one bearing.
 21. A stump cutter comprising: a prime moversupported above a ground surface by a mainframe of the stump cutter; acutter wheel configured to be driven about a cutter wheel axis by theprime mover, wherein the cutter wheel is supported for sweep movementsabout a vertical cutter wheel sweep axis so that the cutter wheel sweepsalong an arcuate path within a horizontal plane, and wherein the cutterwheel is supported for tilt movements about a horizontal cutter wheeltilt axis so that the cutter wheel tilts along an arcuate path within avertical plane; a mechanical driveline between the prime mover and thecutter wheel, the mechanical driveline including a first right anglegearbox including a vertical output shaft defining a driveline sweepaxis parallel to the cutter wheel sweep axis, a second right anglegearbox pivotally mounted on the first right angle gearbox about thedriveline sweep axis, the second right angle gearbox including ahorizontal output shaft defining a driveline tilt axis, a third rightangle gearbox mounted on the second right angle gearbox and including anoutput shaft, and a cutter wheel right angle gearbox having an outputshaft extending along the cutter wheel axis, the cutter wheel rightangle gearbox having an input shaft connected to the output shaft of thethird right angle gearbox.
 22. The stump cutter of claim 21, wherein thevertical output shaft of the first right angle gearbox also forms aninput shaft of the second right angle gearbox, and wherein thehorizontal output shaft of the second right angle gearbox also forms aninput shaft of the third right angle gearbox.
 23. The stump cutter ofclaim 21, further comprising a sweep subframe pivotally connected to themainframe to define the cutter wheel sweep axis, and a tilt subframepivotally connected to the sweep subframe to define the cutter wheeltilt axis, the tilt subframe supporting the cutter wheel right anglegearbox at an end opposite the cutter wheel tilt axis.
 24. The stumpcutter of claim 21, wherein the cutter wheel tilt axis is offset fromthe driveline tilt axis, the stump cutter further comprising a jointeddriveshaft connecting the output of the third right angle gearbox to theinput of the cutter wheel right angle gearbox; and a gearbox alignmentstructure extending along the jointed driveshaft and having a firstportion fixed to the cutter wheel right angle gearbox and a secondportion fixed to the third right angle gearbox and configured to limitmisalignment between the input shaft of the cutter wheel right anglegearbox and the output shaft of the third right angle gearbox.
 25. Thestump cutter of claim 21, wherein the mechanical driveline furtherincudes a clutch operable to selectively connect an output of the primemover with an input of the first right angle gearbox.